Developing a Solar 30A 120VAC System

Yet another new guy with I'm sure a very old question. We are considering purchasing 50 acres in western Texas. No water or electric available on site and it would cost about $15,000 to have electric service ran to the location. This price just gets it there. There are other costs involved to get everything in place and functioning.
We plan on parking a travel trailer on this location that operates on 120VAC 30A service. I'm thinking that rather than spending the +$15K on grid power I could drop that, or a portion of it on a solar/wind system but don't even know where to start.
As far as loads? All I know is that I would most likely operate the A/C quite a bit during the day. I also know that when operating the system on my 3.5KW generator I can run the A/C and either water heater or microwave with no problem but will not run all three without bogging down the gen or tripping the 30A breaker.
I plan on building a 20'X40' cover and will mount the panels on this. There is a hill that I can locate a wind turbine on for rainy days and I have a few generators as well for backup. As mentioned before, drilling a well will required and this will operate on generator.
Where do I even start and is this even a viable option? From what research I have done: 48V system may be the best, 6V GC batt's?, MPPT charge controller, 3KW or better inverter and I'm clueless to the different types of panels.

Comments

At $15,000 for utility power--That is very close to what an off-grid system will cost for an efficient off-grid home.

However, because you may end up using lots of A/C in your region--That is a tremendous load for solar power (and expensive/complex). If you need pumping/irrigation, that even adds to the power requirements.

In general, utility power is around $0.10 to $0.20 per kWH and off grid power is on the order of $1 to $2+ per kWH (very rough numbers, just trying to set expectations).

There are a few people here that have off grid power systems and A/C for their homes. So it can be done (and they are very happy).

As a starting point--we always suggest designing for minimum power usage and heavy conservation. That will help you no matter your final choice in power.

And with solar power, it is very important to have a good handle on your power needs (kWH per month, by season) to ensure you build s system that is large enough to meet your needs/expectations--But not be too large (which makes for an expensive install and long term maintenance).

In general, an efficient off-grid home may use around 100 kWH per month (3.3 kWH per day) (lighting, radio/tv, computer, washer/gas drier, well pump, etc.)... But A/C + irrigation pumping can blow those numbers right out of the water. A typical home in your region may use ~1,000 to 3,000+ kWH per month.

So--what do you estimate your power needs to be? It is very difficult if you don't already have your home there (just read the utility bill)... Power usage is highly personal--And two different families in the same home may have 2-3x different power usage.

There are three load factors that need to be considered in an off-grid system. The first is Voltage. We know that is 120 VAC here. The second is the maximum power draw. We know that is 30 Amps or 3600 Watts. The third is the Watt hours consumed, and that one we don't know.

Try to use propane for any heating instead of electric. Direct solar hot water can be a big help, and certainly ought to work in Texas. Lots of good ideas/plans for that at Build It Solar: http://www.builditsolar.com/

I agree that a 48 Volt system would be best due to the higher peak needs and likely high over-all Watt hours. That last thing is something you need to get a handle on in order to plan the system. The venerable Kill-A-Watt meter can help with anything that plugs in, but hard-wired loads you'll have to do a best estimate on based on the manufacturer's supplied info and some careful timing of your average use.

The $0.10 to $0.20 (I currently pay $0.115 in my full time home) is monthly consumption. Where does the $1 to $2 per kWH solar come from? What maintenance cost is expected on solar once installed?

Thanks

The big number is the cost of generating power from solar in an off-grid scenario.
You have a capital investment of "$X" which buys equipment capable of producing "Y" kW hours over its expected lifetime of "Z" years. Basically "X" divided by "Y" equals the $1 to $2 per kW hour before replacement equipment is needed. The worst of it is the batteries, because their lifespan can be shortened drastically if things aren't right. Chronic under or over charging will cut their useful life down to as little as "working today, scrap metal tomorrow".

For GT and Off Grid--Figure on needing a new inverter after 10+ years.

For Off Grid Systems--Plan on new charge controller every 10+ years.

Batteries, replace every 6-10 years (there are 20 year forklift batteries). More or less, a battery that last 2x longer costs 2x as much. Forklift batteries tend to be slightly less efficient (less power available from solar) and use more distilled water (some costs for water too).

You should plan on a backup genset and fuel (ideally, you can run around ~9 months of the year on solar only, and a mix of solar + genset during the winter). At this point, it will probably cost around $1-$2 per kWH just for fuel.

Remember that for figuring the costs of solar power--The more you use the "less per kWH" it costs. If you have a weekend summer cabin, your system can probably supply 2-3x as much power as you use. If you live 9+ months of the year, you can use ~75% or so of the total output available for the system.

The reasons a generator (and propane fridge) make sense for weekend/summer cabins--You only pay for fuel when you use it.

Batteries also age over time too... A well cared for bank will last about the same length of time if it is used or just sitting at float voltage.

Thanks Caraboocoot
I guess I should clarify that this is a camper we want to power, the 13,500 btu A/C is already installed (roof mount). I just need enough power to run this A/C. I do plan on heating and cooking with propane as well. I can get a wattage reading on each load with a kill-o-watt meter and have no problem doing so if solar power appears to be a viable option.
I'm starting to think paying the man the $15K to drag the grid to me and paying them whatever/month they ask for may be the way to go.

Got it. I was seeing the first 'x' as free. I either pay the power company to run their cable or buy solar equipment with that $$. It's the 'z' that will catch up to me.
Unless I'm missing something solar is a loosing long term investment. I can pay the power company the $15k and then the $0.12/kWH for ever or spend the $15K on solar that will need to be completely replaced in ~10 yrs. The grid wins.

You can buy a pretty big off-grid system for $15k. The big question is the Watt hour consumption. That determines how large a battery bank is needed which in turn dictates the size of the array. The good news is that panel prices are at their nadir right now.

Got it. I was seeing the first 'x' as free. I either pay the power company to run their cable or buy solar equipment with that $$. It's the 'z' that will catch up to me.
Unless I'm missing something solar is a loosing long term investment. I can pay the power company the $15k and then the $0.12/kWH for ever or spend the $15K on solar that will need to be completely replaced in ~10 yrs. The grid wins.

Could be. Especially with higher consumption. My $8,000 (CDN) 2.4 kW hour off-grid system was far cheaper than the impossible cost of running the grid across 15 miles of public and private land. But if the install is straightforward and you need "standard household consumption" potential the grid ends up being cheaper every time.

Of course once you have grid you can install a grid-tied system and possibly get a bit of your own back, depending on how that works in your area.

You may have other utility surcharges for a remote installation (I don't know). And, there may be service charges based on how much energy you use... Example, you may pay a flat $0.12 per kWH for >1,000 kWH per month... If you use 300 kWH per month, you may have some sort of $50 per month service/meter reading charge (just guessing).

You do not have to replace the solar array for 20-40 years or the wiring... So there are some costs that have a longer service life. But, on the other hand, if you have a battery bank and somebody forgets and leaves a bunch of lights on in winter while you are on a trip--You may have a whole battery bank that needs to be replaced.

Owning your own power station has real costs and financial risks that you just don't worry about with grid power.

And, as Marc suggests, you could always research adding Grid Tied Solar (no batteries) down the road (assuming your utility supports GT solar and has a decent (for the customer) rate plan).

the only "standard household consuption" would be the TV, satilite receiver, A/C and microwave. The last two don't need to be operated at the same time and frankly, we rarely use the microwave. The fridge runs on propane or low consumption 120VAC. lighting and furnace blower are 12VDC. The TV can be replaced with a 12VDC unit. Campers are fairly efficient and are designed for long term 12DC operation excluding whats listed above. Regardless, as I suspected the A/C is the off-grid deal breaker. I have already install a soft start cap on the A/C.
I need to get some load values before I blow off solar.

i'll throw a few cents worth in here. this is a close call to me for there are advantages and disadvantages going either way here and there are also gray areas that can evolve too. the bills will come in every month from a utility and could easily exceed any maintenance costs you could encounter with solar and being the last on the line you will tend to be the last to be reinstated too during an outage mandating you have either a generator (you already have, but gas supply could need to be large and possibly unavailable) or a backups (be it solar or not) or both. utility costs are guaranteed to rise as utilities move towards thinking each electron moved is worth its weight in gold. it will be an expensive undertaking no matter what way you go with this. i will say that all pros and cons of every option available to you is too big to get into in my piddly post, but i will say you should have something solar no matter what because every option will boil down to availability and reliability for how long with costs considerations.

edit to add,
this does sound like a nonanswer, but it realy is an answer as it could actually boil down to you and your preferences. options are many and go by max load draw, overall dailly loads in kwh, gasoline costs, genny maintenance costs, of course the initial costs for solar and their longterm costs, how long you can go with any 1 non-utility power source before exhausting it if you can exhaust it, to mention some. and finally in the case of the utility there is their initial costs, their reliability, their monthly bills to you, and their cost increases. i wouldn't blame you if you elected to have all options for your property, but i agree that you need more than just 1. each option throws more cost to an already high cost proposal no matter which one or ones you elect to get with more options gotten making more reliable power available.

'll throw a few cents worth in here. this is a close call to me for there are advantages and disadvantages going either way here and there are also gray areas that can evolve too.

My two cents also. You haven't said or I missed it, is the travel trailer going to be stationary or will it be moved? One thought is to replace your rooftop AC unit with a modern 25 SEER ductless AC with variable speed compressor. They are quite a bit more efficient then what you probably have on your roof. It is a good idea that the trailer will be under the solar shed. I suspect that you can do an off grid system for substantially less then 15K at todays good prices. You can look into a refurbished fork lift battery in the 2K range which will probably last 10 to 15 years, a charge controller and inverter in the 3 to 4k range including wiring, and panels can sometimes be had for as little as a dollar a watt for grade B panels by shopping around. If you can do much of the work yourself and adapt to the power generated, you are looking in the 10K range for a 4KW off grid system. You can spend more or less depending on your skills. There will always be ongoing maintenance on the batteries that must be kept up with monthly.

Thanks for the additional input.
The camper will be mobile. We live about 300 miles away from this location. The intent of the property for now is we will leave the camper there as a weekend getaway. We will go out there once or twice a month and either stay there for 3 to 5 days or hitch up and enjoy some of the camp grounds in the area. Once I retire in about 10 years we have to decide if we continue doing the same, spend more time out there, sell that place, sell our current home and move out there or sell both and move somewhere unrelated to both.

After reading everything off grid all day and thinking more on this, I believe investing in the grid connection would make the place less complicated and more appealing if/when we do sell. The grid would solve powering the water well concern as well. I was considering powering the well pump with a generator to fill the on-board fresh water storage tank and draw off of this tank with the campers 12V pump between runs. Coordinate this fill with battery charging. Grid power eliminates this.

I love the idea of grid independence but I'm realizing the disadvantages and short comings of such a system even with todays technology. In short, the grid would be more appealing to more perspective buyers in the future. I started out this morning looking for a way to keep from giving the power company my money. I'm ending the day convenced it's the smart thing to do in my situation.

It really depends on how much power you will need--There are certainly well pumps (for example) that will operate on a little as 200 watts of solar power. And the mini-splits will operate down to 300 watts of power (of course, that is 1/3rd of rated cooling power of ~3,000 BTU or so).

In the end, if you need a lot of power (full home with AC/Irrigation, etc.)--And if you later sell the property--I would certainly agree that having grid power is probably a positive. You could contact a local real-estate agent that is knowledgeable about your area and ask them how much grid power is "worth" to the value of the property.

Reading this late in the game, but If you can mange to only need the air conditioning while the sun is shining, you would not need a huge battery bank to run it at night.
You can have a decent system with a generator, batteries & inverter/charger. You run the genset a couple hours a day.

Use the parts listed in my .sig, price that out for a 3KW PV system (golf cart batteries work well for a learning set)

Mike90045
Funny you mention Listeroid. I have a 25/2 for house backup. I can pull 8kw out of it with no problem to power my 2200sqf home. I haven't had any issues with mine but I do read the horror stories on the clones. I don't know if I would want another one. I've actually thought of selling my 25/2 for something more modern but I couldn't get out what I have in it so it's a coversation piece until the next hurricane.

Given that costs are likely fairly close, one other factor to consider (speaking as someone who recently built an off-grid PV system in your approximate size-range) is whether an off-grid system is something you'd enjoy building and maintaining, or not really. I've enjoyed designing and building my PV systems (this is my third one), and I like watching them work, tweaking them, and the modest sense of independence they offer. To me, this is a very significant part of the 'return' on the system cost.

But I completely understand that not everyone shares this kind of interest, and solar starts looking to you like a big hassle, I'd say go with the grid.

I've enjoyed designing and building my PV systems, and I like watching them work, tweaking them, and the modest sense of independence they offer. To me, this is a very significant part of the 'return' on the system cost.

And THAT Eric, is exactly the way I feel, especially about my micro hydro. Built the crossflow turbine from scratch, and take great pleasure in doting over the whole hydro system, from the diversion dam, to the pipeline, to the turbine and alternator itself. Together it's a living thing. Some people love the sound of great music, to us, this is great music, and it greatly enriches our lives.
Those who do it only for the money they expect to save, will often be disappointed.

Given that costs are likely fairly close, one other factor to consider (speaking as someone who recently built an off-grid PV system in your approximate size-range) is whether an off-grid system is something you'd enjoy building and maintaining, or not really.
But I completely understand that not everyone shares this kind of interest, and solar starts looking to you like a big hassle, I'd say go with the grid.

Very Good Point. As other projects have proven, I would be all gun-ho jumping into it but at some point before I am complete that labor of love just becomes labor. I'll loose interest, wanting to get it completed and the quality of my labor would show it. I'll start rushing to the finish line.
Another thing I realized is the property is 1900' deep, hilly and heavily treed with large oak and cedar. I'm talking so thick in most places you can't see beyond 30'. We want to place the living quarters in the middle of the property slightly up a west facing hill. The grid comes in from the street. In order to run the line to where we want it I would have to cut a 10' to 15' wide straight line for about 900' or so. This will essentially do what we don't want to do, take out so many trees and alter its natural beauty. I can bring it in along the side to a point and angle it to it's destination but that adds to material cost. And again I have no idea what that cost would be. The $15K gets the grid to the front of the property. Beyond that is an additional charge of unknown. Realizing the unsightly cable and added cost of 'don't know' is starting to lean me back towards solar.
Before you ask, the drive in will meander towards the center laid out with minimal tree removal a priority.

Before you ask, the drive in will meander towards the center laid out with minimal tree removal a priority.

I recommend you reconsider this point now, especially thinking about the materials you will need to bring on site as well as any heavy and not so heavy equipment you will need to 'develop' the property. Also where septic and water lines need to go.
Bin there , dun that, duh, and regretted having to cancel out a lot of hard work in the process.
Long & straight is best so a series of straight sections will give you some of what you.
What you don't want to do is, in a RUSH, have to knock over a few trees or ?? because they are 'in the way' of something that is costing you $120 / hr... or more...

westbranch
Can you elaborate? I need to lay out the drive in a manner to get a 35' trailer in so no sharp turns. I own a John Deere 5075e with front end loader and box blade. The surface is mostly rock and gravel under a thin layer of top soil so limestone or caliche required would be small if any. Placing the septic and water well will be done by the pro's. Ahh, getting the drilling rig and tanks in? Good point. What did I miss? Please share your experience.
Most trees removed will be havested for reuse.

I will state the obvious issue with the trees. Shade kills solar, even a little. If the panels do not have unobstructed view of the sun, they won't produce much. If you are making a clearing to park the RV you would have to be sure that no shade got to the area where the panels go for most of the day. That may require you to take the tops off of some trees, or remove them completely. Trees grow. You have to take that into account also. Go out there at 10 am and see where the tree shadows are and go back at 4pm. At this time of the year you would be surprised how far a shadow can throw.

to keep it as short as possible, you need enough room to turn around a concrete pumper truck, ~ 60 feet with overhangs as well as more room for any truck (tractor unit) that has a trailer behind it , so that they do not have to disconnect the trailer from the tractor and jigg around. Especially if there are 2 or more trucks ie pumper and concrete truck, present at the same time. Turn arounds away from the 'site' are very beneficial.

Thanks westbranch
I don't see pouring concrete out there. The pad location will be stone. I do have to assure the driller and septic guy can get their equipment back there.
The site will be located on a hill and I was thinking of a pull-through configuration. Have the drive go around the back of the cover and drive into it rather than backing into it. Tree's in that immediate area will have to be removed.

After reading more here and other sites this seems to be more doable. One comment I read that seems to apply is more panels and less battery. Run the generator to supplement in the evening.

so you need to start with the loads to size the PV and batteries to minimize the amount of generator time. Now is the time to develop a master plan for modifying/upgrading your system. PV will likely never be this cheap again.
Planning time is never wasted.